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Juno PDS data
Gerald
post Sep 6 2017, 07:11 PM
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I'll try to squeeze it in appropriately during the first half of October, at least partially. I could also take some of the (vast amount of) pretty unstructured material to Riga, and meet with your colleague Michael Ravine. This week, and most of next week, PJ08 processing and preparing the EPSC talk(s) have priority.
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Bjorn Jonsson
post Sep 19 2017, 12:38 AM
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QUOTE (Gerald @ Sep 6 2017, 12:02 PM) *
Unfortunately, I need to deviate from the best fits derived from star positions in order to obtain best-fits of local RGB alignment, the latter two orders of magnitude more accurate. There must still be some unconsidered effect, at least in my models. I hope, that I'll find more time for geometrical calibration near the end of this year. Possibly K3 plays some role near the margins. And I'm inclined to verify, whether there is some small chromatic aberration, and whether the pixels are perfectly square.

k1 and k2 values that result in more accurate RGB alignment would be very useful.

Using the updated radial distortion function parameters (k1 and k2) and focal length from the new JunoCam kernel file has reduced the RGB color alignment errors I'm getting (the updated frame kernel is probably also significant here). After reprojecting the framelets to simple cylindrical projection I usually warp the green and blue channels into the red channel because even an alignment error of just ~2 pixels is noticeable in enhanced/sharpened images - I want 'perfect' alignment. However, when I use the new kernels the alignment errors are smaller than before (I need to process more images to completely confirm this though). The area where I need to warp the GB channels is also smaller (it's near the image edges - close to center the alignment is/was perfect). Some of the alignment errors might be due to slight inaccuracies in the camera pointing parameters I'm using when reprojecting the images.

Regarding a possible small chromatic aberration: Is it possible that the best way to get rid of RGB alignment errors might be to use slightly different k1 and k2 values for the different color channels? Has this been tried?
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mcaplinger
post Sep 19 2017, 02:34 AM
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QUOTE (Bjorn Jonsson @ Sep 18 2017, 04:38 PM) *
Is it possible that the best way to get rid of RGB alignment errors might be to use slightly different k1 and k2 values for the different color channels?

I'd have thought that the focal length would be a larger variable than k1/k2.

Gerald has said that he is getting residuals much smaller than 0.1 pixels. I haven't been able to get anything close to that good, so it would be very useful for him to document his processing in a way that could be incorporated into the I kernel.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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